Loop Antenna Research Articles

Abstract 4119167: Electromagnetic Interference from Electric Vehicles: Implications for Subcutaneous Implantable Cardioverter-Defibrillators

Background: Electromagnetic interference (EMI) refers to signals discernible by a device’s circuitry, potentially resulting in erroneous sensing, pacing, mode switching and defibrillation. EMI poses potential risks to the functionality of cardiac implantable electronic devices, with Subcutaneous- Implantable Cardioverter-Defibrillators (S-ICDs) potentially more susceptible due to their design. Research Question: Does EMI from Electric Vehicles (EV) interfere with the functionality of S-ICDs? Goals: Developing and utilizing a loop antenna device that mimics S-ICDs to assess the susceptibility of S-ICDs to EMI from EVs in different charging conditions. Methods: A loop antenna device mimicking the S-ICD lead design was developed, and then validated by the Food and Drug Administration, to detect electromagnetic signals. The device was positioned at different locations in a Tesla Model 3 to measure electromagnetic signals. Results: Statistical analysis revealed a significant difference (p-value < 0.0001) in detected voltage (400-504 mV) around the cup holder compared to all other measured locations. These signals fell within the R-Wave Spectrum of 30-300 Hz. Conclusion: We identified EV-emitted EMI capable of disrupting S-ICD functionality. Further in-vivo studies are essential to determine the level of interference between S-ICDs and EMI from EVs.

Enhanced RF Energy Harvesting System Utilizing Piezoelectric Transformer

RF energy harvesting converts ambient signals into electrical power, providing a sustainable energy source. This study demonstrates the use of a piezoelectric transformer for efficient RF energy harvesting. In this work, a piezoelectric transformer (PT) is employed as a high-gain, efficient inverting amplifier to enhance RF wireless energy harvesting. The PT, composed of lead zirconate titanate (PZT), is placed after the receiving loop antenna, with its output connected to an AC-to-DC converter circuit. Maximum harvested power was observed at the PT’s resonance frequency of 50 kHz, with an optimal load of 40 kΩ. The system, comprising the antenna, transformer, and rectifier circuit, continues to resonate at 50 kHz, as confirmed by input impedance measurements, demonstrating stable and effective performance. The overall system efficiency was characterized to be 88%.

Analysis of Beamforming for OAM Communication Using Loop Antenna Arrays and Paraboloids

Analysis of Beamforming for OAM Communication Using Loop Antenna Arrays and Paraboloids

A SAW Wireless Passive Sensing System for Rotating Metal Parts

Passive wireless surface acoustic wave (SAW) sensors are very useful for on-site monitoring of the working status of machines in complex environments, such as high-temperature rotating objects. For rotating parts, it is difficult to realize real-time and continuous monitoring because of the unstable sensing signal caused by the continuous change of the relative position of the rotating part to the sensor and shielding of the signal. In our SAW sensing system, we propose a loop antenna integrated with the rotating part to obtain a stable sensing signal owing to its omnidirectional radiation pattern. Methodologies for determining the antenna dimension, system operating frequency, and procedures for designing a SAW sensor tag are discussed in this paper. By fully utilizing the influence of metal rotor on antenna performance, the antenna needs no impedance matching elements while it provides sufficient gain, which equips the antenna with nearly zero temperature drift at a wide temperature-sensing range. Experimental verification results show that this sensing system can greatly improve the stability of the sensing signal significantly and can achieve a temperature sensing accuracy of ~1 °C at different rotational speeds, demonstrated by the feasibility of the loop antenna for monitoring the working status of rotating metal parts.

Advantages of Plate Antennas over Loop Antennas for Circular Polarization—Its Application in Array Antenna with a Simplified Feed

We analyze square antennas with one and quasi-two sources to reveal the relationship between loop and plate antennas. First, using the moment method, one-source antennas with corner truncation are investigated versus antenna height above the ground plane. As the height increases, the CP wave bandwidth of the plate antenna increases 17% for a 3 dB axial ratio criterion, whereas the loop antenna’s bandwidth remains less than 3%. Next, we study quasi-two-source antennas without corner truncation versus antenna height. The plate antenna’s bandwidth is found to reach 30%, which is wider than that of a loop antenna by a factor of two. Last, the plate antenna with quasi-two sources is applied in an array antenna, whose properties are compared to those of the corresponding loop antenna array. We present experimental results to verify the simulated results.

Wireless LED controller IC for smart contact lens system

AbstractThis letter presents a wirelessly powered LED driving circuit for a smart contact lens system. Since photobiomodulation has been investigated for ocular disease treatment by irradiating light with a specific wavelength, a smart contact lens equipped with a µLED and its controller IC can be utilized as a phototherapy system. The proposed circuit design facilitates constant‐current generation to drive the LED and incorporates a wirelessly powered system. The system can be turned on and off in synchronization with an external wireless power source, providing controllability for the LED's irradiation period and intensity. The IC is fabricated in the 180‐nm CMOS process with a die area of 1.0 mm2 and integrated into the smart contact lens with an external loop antenna and a far red/NIR LED. The measurement demonstrates the irradiation period of the LED is successfully controlled by the external source, with current levels from 0.53 mA to 1.4 mA, thereby confirming the feasibility of the phototherapy system.

Measurement of electrical conductivity of human tissue: A feasibility study of a novel time-domain approach

A straightforward, non-invasive experimental approach to the extraction of electrical conductivity of human tissue using the transient electromagnetic field coupling between two loop antennas is presented. The main objective of this initial study is to demonstrate the feasibility of the new time-domain (TD) methodology. The designed loop antennas and the experimental setup with its instrumentation are described. The presented results show that the proposed method is capable of obtaining accurate values of the electrical conductivity of human tissue.

Simulation and Design of Three 5G Antennas

In the context of 5G networks, this paper investigates microstrip array antennas and mobile terminal MIMO array antennas. It introduces two innovative designs and, based on these, develops and fabricates a mobile terminal antenna. The first of these designs, a 4 × 4 microstrip array antenna operating in the LTE band 42 (3.4–3.6 GHz), is researched and fabricated and an innovative approach, combining embedded and coaxial feeding methods, is proposed and employed. Measurement results indicate a bandwidth of 373 MHz (3.321–3.694 GHz), achieving a relative bandwidth of 10.7%. The antenna exhibits a high gain of 12.7 dBi, with an undistorted radiation pattern, demonstrating excellent directional characteristics. The second of these designs, a “loop-slot” MIMO antenna designed for 5G mobile devices with metal frames, is investigated. By opening slots in the metal frame and integrating them into the antenna’s feeding structure, the decoupling principle is analyzed from the perspective of characteristic mode theory. This design shares resonant modes between the loop and slot antennas, allowing for the overlapping placement of the two antenna units. Experimental results confirm an isolation level exceeding 21 dB, with significantly reduced dimensions. Finally, an eight-unit MIMO antenna is designed and fabricated for 5G mobile devices with metal frames. Continuous optimization of the “loop-slot” module layout and unit spacing leads to a compact and miniaturized antenna structure. Measurement results show an isolation level exceeding 17 dB, radiation efficiency ranging from 65.8% to 73.7%, and an envelope correlation coefficient (ECC) below 0.03. Finally, an analysis of specific absorption rate (SAR) demonstrates excellent MIMO performance in terms of human body radiation exposure.

Effect of gas injection pattern on magnetically expanding rf plasma source

Abstract Argon gas is injected from a back plate having either a radial center hole or shower-patterned eight holes into a 13.3-cm-diameter and 25-cm-long radio frequency (rf) plasma source attached to a 43.7-cm-diameter and 65cm-long diffusion chamber under an expanding magnetic field, which resembles the magnetic nozzle rf plasma thruster. The source has a double-turn loop antenna powered by a 13.56 MHz rf generator at a maximum power level of ~2.8 kW in low-pressure argon, providing a plasma density of about 1018 m−3 in the source. A high plasma density and a slightly low electron temperature are obtained for the shower-pattered case in both the source tube and the diffusion chamber, compared with the center hole case, suggesting that the neutral density profile significantly affects the plasma density profile. This result will provide an improvement in the thruster performance by the gas injection pattern.

A Review of the Applications of Through-the-Earth (TTE) Communication Systems for Underground Mines

AbstractUnderground mining accidents have the potential of leaving miners trapped in unknown and life-threatening locations for an extended period of time. The lives of the trapped and unaccounted-for miners are at risk and require emergency rescue. But, the primary tracking systems are highly susceptible to damage during accidents and are most likely to be defunct and inoperable post-accident. This prompted the need for a robust and reliable post-accident communication and locator system. Subsequently, the through-the-earth (TTE) communication systems were developed and tested in underground mines. Under ideal conditions, these systems are capable of post-accident full-duplex two-way voice, text, and data communication and fingerprint detection of the geolocations of the trapped miners. This is achieved through a wireless link established by the transmission of electromagnetic and seismic waves between surface and underground, even in challenged underground environments. Unlike the primary tracking systems, the TTE communication systems do not require extensive shaft-to-workplace backbone infrastructure. This has made the TTE systems to be less susceptible to damage and therefore suitable for post-accident communication. Instead, the Earth’s crust acts as the signal transmission medium which forms an uplink and downlink communication path. This is achieved by injecting an electric current into the ground using electrodes, by transmitting magnetic fields from a radiating loop antenna, or by inducing fingerprint geolocations using seismic waves. Range and data rates are the critical requirements for the effectiveness of these systems and are dependent on factors such as the antenna design, frequency, and rock properties. This study provides a review of the applications of the different types of TTE communication systems, their evolution, factors that affect them, and techniques for improving their efficiencies and capabilities. These systems present the mining industry with an opportunity to improve safety by providing post-accident communication and locating trapped miners as quickly as possible. This will improve their survival chances and ultimately reduce fatality rates in the mining industry.

Characteristics and mechanism of low-field peak in argon helicon plasma of single loop antenna

Characteristics and mechanism of low-field peak in argon helicon plasma of single loop antenna

Wideband Eight-Antenna Array Designs for 5G Smartphone Applications

This paper proposes a broadband eight-antenna array design suitable for Fifth Generation New Radio (5G NR) smartphone applications. To cover the 5G NR bands n77/n78/n79 (3300–5000 MHz) and 5G NR-U n46 band (5150–5925 MHz), the single antenna array unit applied is a modified loop antenna element (MLAE) that can generate three different loop modes. To yield good multi-input multi-output (MIMO) performances, the designed MLAE is further arranged as an eight-antenna array, and the experimental results show that the overlapping 6 dB bandwidth can cover the bands-of-interest (3300–5925 MHz) with good isolation and total efficiency of >10 dB and 51–84%, respectively. Finally, good MIMO performances, such as an envelope correlation coefficient (ECC) of lower than 0.1 and desirable channel capacity (CC) of 37–40 bps/Hz, were calculated across the bands-of-interest.

Design of an electrically small printed square loop antenna for closely spaced Tx/Rx systems

AbstractA highly miniaturised electrically small square loop antenna has been designed for operation at 2.5 GHz. The antenna is loaded using a simple series combination of two lumped inductors and two interdigitated capacitors in order to realise inherent impedance matching at a given miniaturisation level with respect to a specified source impedance, without using any external matching network. The designed antenna has an overall size of 0.061λ0 × 0.061λ0, which is approximately 75.6% miniaturised in terms of total loop length and 94% miniaturised in terms of overall footprint. The designed antenna is fabricated and the corresponding impedance matching and radiation patterns are measured, which are found to be in reasonable agreement with their simulated counterparts. Moreover, an investigation with two closely spaced electrically small SLAs, one for transmitting and the other for receiving, is carried out in this work in pursuit of maximising the isolation, which plays a crucial role in the Tx/Rx systems.

Multimode Balanced Mu-Near-Zero Loop Antenna for Wi-Fi 6/6E Applications in Full Metal Housing Tablet Computers

Multimode Balanced Mu-Near-Zero Loop Antenna for Wi-Fi 6/6E Applications in Full Metal Housing Tablet Computers

Design of a Cavity for the High-Power Radio-Frequency Quadrupole Coupler Test for the ANTHEM Project.

The ANTHEM (Advanced Technologies for Human-centered Medicine) Radio-Frequency Quadrupole (RFQ) will employ eight coaxial power couplers, which will be magnetically coupled to the device through a loop antenna. The coupler design can support up to 140 kW in continuous wave operation. This paper presents the design of the cavity used for high-power testing, with the primary objectives of both optimizing the coupling between the couplers and ensuring operations at the designated operating frequency. Furthermore, the paper encompasses thermal and structural assessments conducted through numerical simulations.

Thin Film Magnetic Sensor for Magnetic Near‐Field Measurement in Wireless Power Transfer System

In this study, we employed a high‐frequency‐driven thin‐film magnetic sensor to precisely measure the magnetic near field with enhanced spatial resolution, a challenge often faced by conventional loop antennas. Our study introduced an innovative approach utilizing this magnetic sensor to assess the magnetic near field in wireless power transfer systems, comparing its performance against that of a loop antenna. Our findings demonstrate that the magnetic sensor achieves its peak signal‐to‐noise ratio at a DC bias field of 4.7 Oe and carrier frequency of 0.5 GHz, boasting a detection limit for magnetic fields of ~0.4 A/m. Moreover, the magnetic field trend measured by the magnetic sensor closely aligns with simulation results, exhibiting sharper changes around the center compared to the loop antenna. These results highlight the superior sensitivity and spatial resolution of the magnetic sensor over conventional loop antennas. By enhancing the reliability of electronic systems across diverse applications, these sensors pave the way for advanced EMI/EMC evaluation techniques. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Electromagnetic force from electric vehicles: Potential electromagnetic interference source for subcutaneous implantable defibrillator.

Electromagnetic interference (EMI) encompasses electromagnetic field signals that can be detected by a device's circuitry, potentially resulting in adverse effects such as inaccurate sensing, pacing, device mode switching, and defibrillation. EMI may impact the functioning of Cardiac Implantable Electronic Devices (CIEDs) and lead to inappropriate therapy. An experimental measuring device, a loop antenna mimicking the implantable cardioverted defibrillator (ICD) antenna, was developed, and validated at the US Food and Drug Administration (FDA) and sent to Wright State University for testing. Two sets of measurements were conducted while the vehicle was connected to a 220-Volt outlet with charging at ON and OFF. Each measurement set involved three readings at various locations, with the antenna oriented in three different positions to account for diverse patient postures. The experiment utilized a Tesla Model 3 electric vehicle (EV), assessing scenarios both inside and outside the car, including the driver's seat, driver's seat floor, passenger's seat, rear seat, rear seat floor, cup holder, charging port (car), and near the charging station. The detected voltage (max 400 to 504 millivolts) around the cup holder inside the car differed from all other measurement scenarios. The investigation highlights the identification of EMI signals originating from an EV) that could potentially interrupt the functionality of a Subcutaneous Implantable Cardioverter-Defibrillator (S-ICD). These signals fell within the R-wave Spectrum of 30-300Hz. Further in-vivo studies are essential to determine accurately the level of interference between S-ICDs and EMI from Electric Vehicles.

Low windage dual‐band omnidirectional antenna for high‐speed aircraft communication application

AbstractThe letter presents a low‐windage omnidirectional antenna for high‐speed aircraft in the UHF and L bands. It combines a planar biconical antenna with a printed tape parasitic branch monopole antenna. Upgrading the traditional restricted‐length biconical antenna to a double‐layer planar design meets the compact, lightweight, and low windage requirements of airborne use. To enhance bandwidth and meet the lightweight, compact criteria of high‐speed aircraft, the planar‐printed monopole antenna integrates parasitic stubs and loop antenna concepts. Experimental results exhibit excellent isolation between antenna elements, with over 15 dB segregation and operational spectrum return loss of 27% and 18% at 10 dB. The voltage standing wave ratio is below 2, with less than 5 dB variation in the horizontal radiation pattern across frequency bands. The antenna, measuring 20 mm × 190 mm × 270 mm and weighing around 0.5 kg, holds great promise for high‐speed aircraft applications.

Study of the characteristics of broadband matching antennas for fifth-generation mobile communications based on new composite materials

The presented research aims to analyze in detail the characteristics of broadband matching antennas specifically designed for 5G mobile communications applications, with an emphasis on innovative composite materials. The study focuses on a compact planar loop antenna designed for use on smartphones, covering the LTE/WWAN frequency bands 824 to 960 MHz, 1,710 to 2,690 MHz, and 3,300 to 3,600 MHz for full coverage of modern 5G networks. Experimental and numerical methods are used to broadly analyze the frequency range associated with 5G networks. The features of the use of composite materials in the implementation of antenna devices in 5G technologies are noted. A broadband matching circuit (BMC) with elements with lumped parameters and a reduced sensitivity invariant has been synthesized. A 3D model of the adaptive selective surface controller (SSC) was developed using CST Studio. The study results highlight the benefits of new composite materials in improving the performance of 5G antennas. This research makes a significant contribution to the development of 5G technologies by optimizing antenna design for efficient data transmission in modern mobile networks and can be a valuable resource for engineers and designers working in this field.

Design of TE-polarized resonant Bessel-beam launchers for wireless power transfer links in the radiative near-field region

Abstract Resonant Bessel-beam launchers (BBLs)are radiating devices constituted by a cylindrical metallic cavity with a partially reflecting sheet (PRS) on top. Millimeter-wave resonant BBLs typically exhibit transverse magnetic (TM) polarization due to the use of coaxial probes as feeders and homogenized metasurfaces as PRS. Launchers showing either a purely transverse electric (TE) or a hybrid (quasi-TE) polarization have recently been proposed for realizing wireless power transfer (WPT) links in the radiative near-field region at millimeter waves. The former are obtained by means of a radial slot array as a feeder and a homogenized metasurface as a PRS. The latter are obtained by using a loop antenna as a feeder and an annular strip grating in the homogenization limit as radiating aperture. In this work, based on an original semi-analytical model, such a metasurface is demonstrated to show a dichroic behavior. This interpretation explains the improvement in terms of polarization purity with respect to more nondichroic conventional homogenized metasurfaces. The behavior of the annular strip grating under a pure TM polarization is tested with a coaxial feeder, whereas its behavior under a pure TE polarization is tested by means of the radial slot array feeder. Results confirm the validity of the proposed analysis, which is finally exploited to evaluate the WPT performance.